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Abstract

Fourteen sucrose-positive Aeromonas jandaei-like isolates from fresh water and reared European eels were subjected to a polyphasic study to determine their taxonomic position. Numerical taxonomy was used to analyse phenotypic data obtained for these isolates and 43 type and reference strains representative of recognized Aeromonas species. The A. jandaei cluster (phenon 1) was defined at 81·6 % similarity (SJ); this included the A. jandaei-like isolates, the sucrose-positive strain Aeromonas veronii biogroup sobria CECT 4910 and nearly all A. jandaei reference strains used in the study. Four other reference strains of A. veronii biogroup sobria and the type strain of Aeromonas ichthiosmia were peripheral to the A. jandaei cluster. The supra-group ‘A. jandaei–A.veronii biogroup sobria–A. ichthiosmia’ was linked at 80·7 % similarity (SJ) and was clearly segregated from the phenotypic core of the A. veronii biogroup sobria species, which was related to the reference strain Popoff 224 (CECT 4835). DNA relatedness between strains grouped in the A. jandaei cluster (phenon 1) and A. jandaei CECT 4228T ranged from 70 to 100 %, but was below 50 % when DNAs from A. veronii biogroup sobria CECT 4835, A. veronii biogroup veronii CECT 4257T and A. ichthiosmia CECT 4486T were used. In addition, DNA relatedness between peripheral A. veronii biogroup sobria strains and the species A. jandaei (CECT 4228T), A. veronii (CECT 4257T, CECT 4835) and A. ichthiosmia (CECT 4486T) was always below 54 %, as it was between the species A. ichthiosmia (CECT 4486T) and A. veronii (CECT 4257T, CECT 4835). Emendation of A. jandaei is proposed; this taxon now includes sucrose-positive clinical and environmental strains as well as environmental isolates that are pathogenic for fish and humans. Other new traits for this species are the ability to grow at 4–42 °C, acid production from glycerol but not from lactose, d-melibiose or d-raffinose, the use of d-gluconate, l-glutamate or l-proline but not l-lactate, l-alanine, l-arabinose or l-arginine, hydrolytic activity against casein, elastin, starch and lecithin and the inability to lyse arbutin. The DNA G+C content of A. jandaei is also reported for the first time; it ranges from 58·1 to 61·1 mol%. On the other hand, the DNA relatedness data support the classification of peripheral reference strains of A. veronii biogroup sobria outside this taxon, indicating that biogroup sobria requires further revision.

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